The 1972National League Championship Series was played between the Cincinnati Reds and the Pittsburgh Pirates from October 7 to 11. Cincinnati won the series three games to two to advance to the World Series against the Oakland A's. The Reds became the first team in major league history to advance to the World Series without the best record in their respective league, made possible by the Junior and Senior Circuits each splitting into two divisions in 1969. In the previous three post seasons, the team with the best record in each league advanced to the World Series.

The 1972 NLCS ended with a dramatic ninth inning in the fifth and deciding game. Cincinnati catcher Johnny Bench tied the game with a leadoff home run in the inning, and George Foster would later score the winning run on a wild pitch by Pittsburgh's Bob Moose. The series was also notable as the last on-field appearance by Pittsburgh's Roberto Clemente, who would die in a plane crash on December 31.

The Reds got a first-inning homer from second baseman Joe Morgan to take a short-lived 1–0 lead. But Pittsburgh bounced back with three in the bottom of the inning, highlighted by an RBI triple from Al Oliver and an RBI double from Willie Stargell. Pittsburgh never looked back, getting a two-run homer from Oliver in the fifth and coasting to the win behind the strong pitching of Steve Blass. The frustrated Reds ultimately stranded eleven baserunners, and their manager Sparky Anderson was ejected in the fourth inning. The time of game was a brisk 1:57.

Cincinnati bounced back to even the series with a much tighter win in Game 2. Pittsburgh starter Bob Moose, who would suffer an even worse fate in the final game of the series, got nobody out as the Reds began the game with five straight hits. Bobby Tolan and Tony Pérez both hit two-run doubles to give the Reds a 4–0 lead and chase Moose. The Pittsburgh bullpen stopped the Reds offense, though, and the Pirates came back to make it a 4–3 game with single runs in the fourth, fifth and sixth, as Milt May, Roberto Clemente and Dave Cash picked up RBIs. Joe Morgan homered in the eighth to give the Reds a crucial insurance run, and Cincinnati reliever Tom Hall finished a long and strong relief stint to get the victory.

The series moved to Cincinnati and produced a tense, low-scoring contest. Cincinnati's Darrell Chaney and Bobby Tolan hit RBI singles to open the scoring in the bottom of the third. The Pittsburgh hurlers would shut down the Reds offense for the remainder of the game, however, while the Pirates managed just enough hitting of their own. In the fifth Pittsburgh catcher Manny Sanguillén homered to get his team on the board, and Rennie Stennett tied the game in the seventh with an RBI single. The Pirates scored the go-ahead and decisive run in the eighth on a groundout by Sanguillen. Pirates closer Dave Giusti, who would yield a memorable homer in Game 5, came on in the eighth to get the save. Pittsburgh was now just one win from a series victory.

The Reds evened the series with an easy win in Game 4 behind a sparkling two-hitter from Ross Grimsley. The Reds got three early runs off Pirates starter Dock Ellis, aided by Pittsburgh errors in the first and fourth. Grimsley himself singled in another run in the sixth and the Reds eventually added three more. Grimsley hardly needed the extra runs as he shut down the Pirates almost completely, allowing only two hits, both by Roberto Clemente. Pittsburgh got their only run on a seventh-inning homer by Clemente, the last he would ever hit.

Game 5 proved to be one of the most memorable postseason contests in baseball history. Pittsburgh took an early 2–0 lead with second-inning RBIs from Richie Hebner and Dave Cash. The Reds got one back in the third on an RBI double by Pete Rose. But Pittsburgh inched further ahead with another run-scoring hit from Cash in the fourth. César Gerónimo cut the Pirates' lead to 3–2 with a homer in the fifth, and the pitchers for both teams kept any more runs off the board until the bottom of the ninth.

With Pittsburgh needing only three outs in the ninth to get to the World Series, Pirates closer Dave Giusti yielded a dramatic game-tying homer to Johnny Bench on a hanging change-up. The inning rapidly turned chaotic for the Pirates. Tony Pérez singled and was replaced by pinch-runner George Foster. Denis Menke followed with another single, and the Pirates replaced Giusti with Game 2 starter Bob Moose. A fly ball out advanced Foster to third. After Darrell Chaney made the second out on a popup with nobody scoring, Moose threw a wild pitch to pinch-hitter Hal McRae. Foster came home with the winning run amid wild scenes of jubilation in the stadium. The Reds went on to the World Series where they would lose to the Oakland A's, the first of three consecutive World Series championships for Oakland.